1. Field of the Invention
This invention relates to a connection structure for connecting a covered wire and a terminal, wherein a covered wire is placed on a terminal and a cover portion thereof is melted and removed by pressing and applying ultrasonic vibration, so that the core elements of the covered wire and in terminal are conductive contact with each other, and a connection method thereof.
2. Description of Relevant Art
This kind of art has been disclosed in, for example, Japanese Patent Publication No.7-70345. FIGS. 1 show that invention. FIG. 1A shows a first member 1 and a second member 2. The members 1, 2 are made of material (plastic) which can be fused by ultrasonic vibration. The first member 1 contains groove portions 3, and the second member 2 has convex portions 4 which engage the groove portions 3.
FIGS. 1B, 1C show a state in which a terminal 7 is contained in the groove portion 3 and a covered wire 8 is placed thereon. On a bottom face of the groove portion 3 are provided small concave portions 3a and a top face of a convex portion 4 has small protrusions 4a which engage the small concave portions 3a.
According to this art, as shown in FIGS. 1B, 1C, the terminal 7 is incorporated in the groove portion 3 and a covered wire 8 is placed thereon. The second member 2 is placed on the top face of the first member 1 so that the protrusions 4 are inserted into the groove portions 3. While applying a pressing force between the first and second members 1, 2, ultrasonic vibration is applied so as to melt the cover portion of the covered wire 8 nipped between the protrusion 4 and the groove portion 3. Consequently, the core elements of the covered wire 8 and terminal 7 come into conductive contact contact with each other. At the same time, the first and second members 1, 2 are fit to each other by fusion so as to obtain an integrated connection structure as shown in FIG. 1D.
However, according to the aforementioned prior art, and as shown in FIG. 2, the core elements 8a retreat together with the melted cover portion 8b into a gap provided between the groove portion 3 and a side face of the protrusion 4, so that sometimes, it is not possible obtain excellent conductive contact between the core elements 8a and the terminal 7.
As a countermeasure for solving that problem, a method of eliminating a gap between the groove portion 3 and the side face of the protrusion 4 as shown in FIG. 3 can be considered. However, if the groove portion 3 and the side face of the protrusion 4 are in contact with each other, ultrasonic wave is not transmitted properly to target positions (covered wire 8 on the terminal 3) so that processing efficiency deteriorates. Further, because escape of the melted cover portion 8b is limited to the length direction of the groove portion 3, the engagement between the first and second members 1, 2 becomes incomplete, so that there is a fear that excellent conductive contact between the core elements 8a and terminal 7 cannot be obtained.